1. Field
The disclosed embodiments relate generally to the field of communications, and more specifically to methods and apparatus for automatically terminating a call in a communication system.
2. Background
The field of communications has many applications including, e.g., paging, wireless local loops, Internet telephony, and satellite communication systems. An exemplary application is a cellular telephone system for mobile subscribers. (As used herein, the term “cellular” system encompasses both cellular and personal communications services (PCS) system frequencies.) Modern communication systems designed to allow multiple users to access a common communications medium have been developed for such cellular systems. These modern communication systems may be based on code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), space division multiple access (SDMA), polarization division multiple access (PDMA), or other modulation techniques known in the art. These modulation techniques demodulate signals received from multiple users of a communication system, thereby enabling an increase in the capacity of the communication system. In connection therewith, various wireless systems have been established including, e.g., Advanced Mobile Phone Service (AMPS), Global System for Mobile communication (GSM), and some other wireless systems.
In FDMA systems, the total frequency spectrum is divided into a number of smaller sub-bands and each user is given its own sub-band to access the communication medium. Alternatively, in TDMA systems, each user is given the entire frequency spectrum during periodically recurring time slots. A CDMA system provides potential advantages over other types of systems, including increased system capacity. In CDMA systems, each user is given the entire frequency spectrum for all of the time, but distinguishes its transmission through the use of a unique code.
A CDMA system may be designed to support one or more CDMA standards such as (1) the “TIA/EIA-95-B Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System” (the IS-95 standard), (2) the standard offered by a consortium named “3rd Generation Partnership Project” (3GPP) and embodied in a set of documents including Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214 (the W-CDMA standard), (3) the standard offered by a consortium named “3rd Generation Partnership Project 2” (3GPP2) and embodied in “TR-45.5 Physical Layer Standard for cdma2000 Spread Spectrum Systems” (the IS-2000 standard), and (4) some other standards.
In the above named CDMA communication systems and standards, the available spectrum is shared simultaneously among a number of users, and techniques such as soft handoff are employed to maintain sufficient quality to support delay-sensitive services, such as voice. Data services are also available. More recently, systems have been proposed that enhance the capacity for data services by using higher order modulation, very fast feedback of Carrier to Interference ratio (C/I) from a mobile station, very fast scheduling, and scheduling for services that have more relaxed delay requirements. An example of such a data-only communication system using these techniques, is the high data rate (HDR) system that conforms to the TIA/EIA/IS-856 standard (the IS-856 standard).
In contrast to the other above named standards, an IS-856 system uses the entire spectrum available in each cell to transmit data to a single user at one time. One factor used in determining which user is served is link quality. By using link quality as a factor for selecting which user is served, the system spends a greater percentage of time sending data at higher rates when the channel is good, and thereby avoids committing resources to support transmission at inefficient rates. The net effect is higher data capacity, higher peak data rates, and higher average throughput.
Systems can incorporate support for delay-sensitive data, such as voice channels or data channels supported in the IS-2000 standard, along with support for packet data services such as those described in the IS-856 standard. One such system is described in a proposal submitted by LG Electronics, LSI Logic, Lucent Technologies, Nortel Networks, QUALCOMM Incorporated, and Samsung to the 3rd Generation Partnership Project 2 (3GPP2). The proposal is detailed in documents entitled “Updated Joint Physical Layer Proposal for 1xEV-DV”, submitted to 3GPP2 as document number C50-20010611-009, Jun. 11, 2001; “Results of L3NQS Simulation Study”, submitted to 3GPP2 as document number C50-20010820-011, Aug. 20, 2001; and “System Simulation Results for the L3NQS Framework Proposal for cdma20001x-EVDV”, submitted to 3GPP2 as document number C50-20010820-012, Aug. 20, 2001. These are hereinafter referred to as the 1xEV-DV proposal.
All of the aforementioned standards do not include a feature that enables automated termination of a call attempt. A call is a connection between two endpoints in a communications system. At one endpoint, a first user (also called a calling party) on a first subscriber station initiates a call. At another endpoint, a second user (also called a called party) on a second subscriber station receives an indication of the incoming call. In addition, the second user may also receive an indication of the identity of the first user, which the second user is able to determine if the second subscriber station has a caller-ID feature (or equivalent feature).
Typically, the second user will hear a ring on the second subscriber station indicating an incoming call. A first user may want to merely ring the second user and not talk with the second user. In this case, the first user tries to manually terminate the call by for example “hanging up” on the second user before the second user answers the call. However, the second user may answer the call before the first user manually terminates the call, which frustrates the first user's purpose for initiating the call. Thus, there is a need in the art for a feature that enables automated termination of a call, which would enable users to ring other users without risking that the call would be answered.